V
AUTHOR: ALBERT EINSTEIN
DATE: 1916
Indisputably the most famous scientific paper of the twentieth century, Albert Einstein’s General Theory of Relativity ushered in a new scientific age, with implications for the world both good and bad. It demanded a reappraisal of our fundamental understanding of the nature of time and space and showed us that gravity does not function quite as Isaac Newton had envisaged. It also prompted a complete rethink of how we viewed the universe, from the subatomic level up. Among the many outcomes of his work, he laid the groundwork for modern quantum mechanics (although he questioned the concept for the duration of his life) and ushered in the nuclear age, a legacy with which he subsequently always struggled.
For a long while, it seemed unlikely that Einstein would make much of a mark on the world, let alone become perhaps the most famous scientist who has ever lived (and definitely the most recognizable). Born in 1879, he was a late developer when it came to speaking and was nicknamed ‘the dopey one’ by his own father. Although it was soon clear he was gifted in the areas of maths and physics, his academic career stuttered. After graduating from the Swiss Federal Polytechnic School in Zürich, he struggled to find an academic posting. Instead, he took a day job at the Swiss Patent Office, exploring his passion for theoretical physics in his own time.
Then, in 1905, over the course of a series of revolutionary papers, he announced himself to the world – a full decade before publication of the General Theory. The first paper, which he described as ‘very revolutionary’, dealt with radiation and the energy properties of light, and would prove crucial to the development of quantum theory. The second was on the ‘determination of the true size of atoms’ and the third was an investigation of Brownian motion using statistical analysis that confirmed the actual existence of atoms and molecules. The fourth, meanwhile, was the Special Theory of Relativity, which examined the electrodynamics of moving bodies and, according to Einstein in a letter to a friend at the time, ‘employs a modification of the theory of space and time’. It is difficult to think of a more understated way to announce that you are about to fundamentally change humankind’s understanding of the universe.
Einstein established that the laws of physics are the same for all observers moving at constant velocity relative to each other, and that the speed of light in a vacuum is constant. He envisaged a cosmos in which the familiar three dimensions of space meld with time to form ‘spacetime’, where single events may appear to occur at different times to different observers. In layman’s terms, where Newton had seemingly shown that space and time were absolute, Einstein showed that they were not. This was every bit as earth-shattering as anything Copernicus or Darwin had thrown at an unready world. Here was a scientist saying that not even the way your clock ticked or the space it inhabited on your mantelpiece were quite as they seemed. But where others saw uncertainty, he saw unchangeability in the nature of fundamental physical laws. Indeed, he had originally planned to call the paper the Theory of Invariance.
The Special Theory led on to one final paper that year, just three pages long. Its conclusions, though, were startling. Einstein had found that a body’s mass is a proportional measure of its energy content. In other words, mass and energy are different presentations of the same thing. An insight that would come to be illustrated with the most famous equation in history: E=mc2 (energy = mass × the speed of light squared). This discovery – that something very small could contain an awful lot of energy – was the stepping stone to the nuclear age.
Even as the rest of the world was trying to come to terms with the revelations contained within the Special Theory, Einstein was obsessing over its shortfalls. Specifically, he was unhappy that it applied only under circumstances of motion at constant velocity. Furthermore, Newton’s universe relied on the notion that gravity is an instantaneous force but Einstein realized this could not be right since he had established that nothing (including a physical interaction such as gravity) could travel faster than the speed of light.
Many of his greatest intellectual breakthroughs came as a result of complex thought experiments, which he conducted in search of ‘great leaps forward of the imagination’. On this occasion, he focused on the sensations experienced by a person free-falling while contained in an enclosed space such as an elevator. The subject, he came to realize, would have no idea whether they were in the grip of a gravitational field or in gravity-free deep space. It would take Einstein a further gruelling eight years, but from this thought experiment would grow the General Theory.
THE NOBEL PRIZE
Einstein was awarded a Nobel Prize for his work but not, as you might expect, for his work on relativity. In 1921, the awarding committee was unable to reach agreement as to whether his theory qualified for the Prize, as under Nobel rules it needed to be classed as a ‘discovery or invention’. There was a vocal body that argued it was not a ‘law’ that had been ‘discovered’, but a ‘theory’ that had been ‘proposed’. So, a compromise was reached and he was instead given the Prize for the first of his 1905 papers on the law of the photoelectric effect, rather than for the theory that was famous the world over.
One of the chief problems he faced was that his theory required new types of mathematics, including a form of geometry that went beyond that which Euclid had defined. In the end, an old student friend, Marcel Grossmann, came to the rescue, navigating him through the non-Euclidean mathematics of Bernhard Riemann (1826–66) and the calculus of Gregorio Ricci-Curbastro (1853–1925).
By the end of 1915, Einstein was confident that he had suitably refined his theory and had the maths to back it up. Over a series of four lectures that year he laid out what he considered to be ‘the most valuable discovery of my life’. Where Newton described a universe in which an apple falls to the ground from a tree because gravity exerts a force of attraction, Einstein redefined gravity as a curvature of space-time.
Four years later, the first observable evidence for his postulations was recorded and overnight he went from being a moderately renowned figure of modern science to a global superstar whose name resonated in even the least scientific households. As he himself explained it: ‘The practical man need not worry … From the philosophical aspect, however, it has importance, as it alters the conceptions of time and space which are necessary to philosophical speculations and conceptions.’
Einstein carried on his theoretical explorations even as he became an international public figure. Alongside the science, he became a notable campaigner against authoritarianism and also against the atom bomb that he unintentionally helped to create. Today, the impact of the General Theory is around us, everywhere. It is there in how we have come to perceive ourselves within the universe. It is in the mysteries of the black holes that his science predicted. But it is also there in the everyday, in our televisions and the GPS systems that steer our cars. In fellow physicist Max Born’s estimation, the General Theory was nothing less than ‘the greatest feat of human thinking about nature – the most amazing combination of philosophical penetration, physical intuition and mathematical skill’.